The present invention relates to an image data processing apparatus and method, and a provision medium, and more particularly to those adapted to calculate, in converting the number of pixels to change the size of an image to be displayed, post-conversion pixel data according to the area ratio of two image pictures superposed mutually, on the assumption that the size of the pre-conversion image and the size of the post-conversion image are equal to each other.
FIG. 13 is a block diagram showing an exemplary configuration of a conventional image display system. Image data generated in a personal computer 1 is outputted therefrom to a display unit 2 and an LCD (Liquid Crystal Display) projector 4 via a pixel number converter 3.
In case the number of pixels composing a picture on the LCD projector 4 is different from the number of pixels composing a picture on the display unit 2, the image data outputted to the LCD projector 4 is processed in the pixel number converter 3 where the number of its pixels is converted, and then the converted image is projected onto an unshown screen or the like. The pixel number conversion executed by the pixel number converter 3 is performed in a nearest neighbor mode, a bilinear mode or a cubic mode.
Here, an explanation will be given on an example of converting a VGA (Video Graphics Array) format of 640xc3x97480 pixels into an XGA (extended Graphics Array) format of 1024xc3x97768 pixels in a cubic mode, i.e., an example of converting 5 pixels into 8 pixels.
In the cubic mode, the weighting function shown in FIG. 14 is employed to convert the number of pixels. In the example of FIG. 14, it is assumed typically that the width of 5 VGA pixels and the width of 8 XGA pixels are dimensionally equal to each other. And when determining pixel data such as chroma of the 4th XGA pixel, the weighting function is so set that its maximum value is positioned in the 4th XGA pixel.
With regard to the weighting function thus set, the data of the 4th XGA pixel is determined by executing a convolutional calculation by the use of a numerical value which is obtained at the intersection of the weighting function with the perpendicular line drawn from each of the 5 VGA pixels to the weighting function.
In converting an original pixel array into a desired pixel array, the above-described pixel number conversion according to the cubic mode or the like is performed with reference to a plurality of pixels for determining the data of one pixel, so that any image whose chroma is sharply changed as in a character string is affected harmfully by unrelated pixels to consequently cause some blur or deformation of the characters.
It is therefore an object of the present invention to provide improvements capable of realizing, in conversion of the number of pixels, superior conversion of any image of character or the like by adopting the common image information, such as the area ratio for example, shared by a plurality of pre-conversion pixels with a post-conversion subject pixel.
According to an aspect of the present invention, as defined in the appended claim 1, there is provided an image data processing apparatus which comprises a first storage means for storing the input pixel data of a first image; a second storage means for storing coefficients of plural calculation expressions; a select means for selecting a desired calculation expression corresponding to the position of the pixel in the second image; and a calculator means for calculating the pixel data of the second image by using the pixel data of the first image read out from the first storage means to be used in a calculation of the expression selected by the select means, and also by using the coefficients read out from the second storage means to be used in the calculation of the expression selected by the select means.
The calculation expression is determined by the pixel array pattern of said first image corresponding to a subject pixel of said second image when the picture of said first image and the picture of said second image, which are mutually equal in size, are superposed on each other, and said coefficient is determined by common image information shared by the subject pixel of said second image and the relevant pixel of said first image corresponding to said subject pixel.
The common image information is an area ratio.
The select means divides said second image into blocks composed of a predetermined number of pixels, and selects, per block, the calculation expression corresponding to the position of the pixel in said second image.
According to another aspect of the present invention, as defined in the appended claim 5, there is provided an image data processing method which comprises a first storage step of storing the input pixel data of a first image; a second storage step of storing coefficients of plural calculation expressions; a select step of selecting a desired calculation expression corresponding to the position of the pixel in the second image; and a calculation step of calculating the pixel data of the second image by the use of the pixel data of the first image, read out from the first storage step, to be used in a calculation of the expression selected at the select step and also by the use of the coefficients, read out from the second storage step, to be used in a calculation of the expression selected at the select step.
And according to a further aspect of the present invention, as defined in the appended claim 6, there is provided a provision medium for providing a program readable by a computer to execute a predetermined process which comprises a first storage step of storing the input pixel data of the first image; a second storage step of storing coefficients of plural calculation expressions; a select step of selecting a desired calculation expression corresponding to the position of the pixel in the second image; and a calculation step of calculating the pixel data of the second image by the use of the pixel data of the first image, read out from the first storage step, to be used in a calculation of the expression selected at the select step and also by the use of the coefficients, read out from the second storage step, to be used in a calculation of the expression selected at the select step.
In the image data processing apparatus of claim 1, the image data processing method of claim 5 and the provision medium of claim 6, the input pixel data of a first image is stored while coefficients of plural calculation expressions are stored, then a desired calculation expression corresponding to the position of the pixel in the second image is selected, subsequently the pixel data of the first image to be used in a calculation of the selected expression is read out while the coefficients to be used in a calculation of the selected expression are read out, and thereafter the pixel data of the second image is calculated by the use of the read pixel data and the read coefficients.
The above and other features and advantages of the present invention will become apparent from the following description which will be given with reference to the illustrative accompanying drawings.